154 Mr. Taylor's description of the 



support they may afford to any hypothesis on the formation of 

 the rocks or the veins, though they may offer some hints on the 

 subject. 



Imperfect as this sketch is, it may serve to lead the attention of 

 some more able member of the Society to the consideration of the 

 appearances of this district, which I thought sufficiently curious to 

 encourage an attempt at their description. 



POSTSCRIPT, 



December , 1816. 



I have lately visited the tunnel in consequence of its completion, 

 and therefore am enabled to complete the section of the hill, shew- 

 ing that no new strata have been discovered since the preceding 

 paper was written. 



I have likewise ascertained more satisfactorily the dip or under- 

 lay of the lodes near the centre of the hill, and inserted them in 

 the section with two cross lodes or cross courses, which traverse 

 the lodes near that place. A remarkable alteration in the texture 

 of the killas occurs on each side of one of these cross courses, it is 

 found in such a decomposed state that it is converted into a soft 

 clayey matter, so as to be very difficult to preserve a passage through 

 until it can be securely arched. 



A period of thirteen years has been occupied in bringing this 

 great work to a conclusion, and it has not been done without the 

 anxieties consequent on such an undertaking. 



Two things of great importance in the practice of mining may 

 be remarked of this work. First, the extreme accuracy of the line 



